It may surprise many that the Qur'an parallels a passage in the Talmud, specifically a rabbinical commentary in the Book of Sanhedrin.

Talmudic Mishnah

For thus we find in the case of Cain, who killed his brother, that it is written: the bloods of thy brother cry unto me: not the blood of thy brother, but the bloods of thy brother, is said — i.e., his blood and the blood of his [potential] descendants. (alternatively, the bloods of thy brother, teaches that his blood was splashed over trees and stones.) For this reason was man created alone, to teach thee that whosoever destroys a single soul of israel, scripture imputes [guilt] to him as though he had destroyed a complete world; and whosoever preserves a single soul of israel, scripture ascribes [merit] to him as though he had preserved a complete world. Furthermore, [he was created alone] for the sake of peace among men, that one might not say to his fellow, 'my father was greater than thine, and that the minim might not say, there are many ruling powers in heaven;

Qur'anic Verse

“Because of this, we decreed for the Children of Israel that anyone who murders any person who had not committed murder or horrendous crimes, it shall be as if he murdered all the people. And anyone who spares a life, it shall be as if he spared the lives of all the people.

a. The Qur'an itself admits to the borrowing, with the phrase, 'We decreed (katabnā) for the Children of Israel…’

This word katabnā كَتَبْنَا is from the same Arabic root as kitāb, meaning book, as in 'People of the Book', and the verb katabā literally means he wrote. It is used a few verses later (wakatabnā) in Quran 5:45 regarding some things that are certainly in the written Torah, and in another example Quran 7:145 it is used for Allah writing on the stone tablets. Lane's Lexicon includes 'prescribed', 'ordained' among its definitions for this verb [1], though it is likely that this usage arose from royal decrees and legal rulings being written down. In some other verses exactly the same word is translated 'We have written'. It is quite obvious that the author believed that this 'decree' was in the law book of the Jews, the written Torah.

b. The Sanhedrin parallel is not in the Torah as it is merely a rabbinical commentary on Cain’s murder of Abel, derived from the use of the plural, "bloods", in Genesis 4:10. It is a Mishnayot – a teaching of a Jewish sage. Thus, it cannot be of divine origin.

c. The Qur'anic verse relates to the story of Cain's murder of Abel Quran 5:27-31, as does the Sanhedrin parallel.

Muslim Objections

Some Muslims (e.g. Dr Saifullah) claim that the parallelism is inexact, as the Sanhedrin 37a should be limited to ‘whoever destroys a single soul of Israel’. They claim that since the Qur'an lacks this reference to the 'single soul of Israel' but instead, generalizes the injunction to any soul, then the charge of parallelism has failed.

Muslim Objections Refuted

Dr Saifullah has made a number of errors here:

No one claims the parallelism is an ‘exact copy’. That’s why the term ‘parallelism’ is used. By implying thus, Dr Saifullah has created a straw man argument.

The commentary also appears in the Jerusalem Talmud, Sanhedrin 4/5, which omits the phrase, ‘of Israel’. There is no evidence that Muhammad had to rely on the Babylonian Talmud and not the Jerusalem Talmud, even though the former is considered more authoritative. Thus, Dr Saifullah has committed another straw man argument.

Prima facie - this is a clear-cut case of Muhammad erroneously thinking the Sanhedrin 37a is from the Torah and therefore, he included it in the Qur'an. There is no other explanation for the phrase, ‘We decreed / have written’ (katabna) in the verse. If Allah had indeed decreed/ordained/prescribed/made binding/written for the Children of Israel where is the corresponding verse in the Torah? The claim that it is lost because the Torah is corrupted stretches credulity because the parallelism exists in the Talmud, and it is unlikely that something lost from the Torah should find its way almost unchanged into the Talmud as a commentary of a narrative (i.e. a mishnayot). If the Rabbi had in mind a verse in the Torah that has since been lost, why does he quote verbatim from Genesis 4:10 ('it is written...'), but then when making his main point not quote directly this hypothetical lost verse? It is not a law, despite being in the Talmud (Oral Law) but a commentary by a Jewish sage, who explains his reasoning.

Thus, it seems perplexing that Allah should katabna / decreed / ordain / prescribe / write something that is a commentary written by a Jewish Rabbi.